1. Field of Invention
This invention relates to shielding the needle points of hand-held hypodermic needle and syringe injection devices, thereby increasing user convenience and reducing the spread of infectious disease due to accidental needle pricks.
2. Discussion of the Problem
The Washington Post reported in 1987 that on an average day 2,200 American health care workers suffer accidental hypodermic needle punctures.
The two obvious dangers associated with accidental needle punctures are infectious injury and death by disease. The Center for Disease Control says that 200 to 300 health care workers die annually because of the direct or indirect consequences of occupationally acquired hepatitis B, and that annually 12,000 become infected with the disease. At least 20 other pathogens are transmitted by needle puncture, including AIDS.
Accidental needle sticks produce other serious but less obvious consequences. Even if an accidental needle puncture does not transmit disease, health care workers and their spouses or sexual partners suffer long-term psychological injury waiting for test results and anticipating the onset of disease. Significant amounts of time are lost from work because of mental suffering, and reduced on-the-job efficiency results merely from being preoccupied with the possibility of disease transmission.
Infectious needle sticks raise health care insurance rates and increase workers' compensation insurance claims and rates. On-the-job friction between workers and employers takes place as an awareness of the dangers of needle sticks is heightened and some workers become irritated by what they perceive as a lack of concern for their well-being.
And now the costly potential for products liability litigation looms larger against against manufacturers and suppliers of traditional hypodermic injection devices as new safer designs become more practical, especially if such alternative designs are not at least made available as an option to potential plaintiffs.
Because of the vast numbers used, hand-held, single-use, disposable hypodermic needle and syringe devices are the single largest causitive instrumentality of accidental puncture injury in the heath care setting. But the greatest percentage of accidental needle sticks from these devices occur not during their primary use during the injection process. It is during the preparation of these devices for disposal, or during disposal, or after disposal, that the greatest percentage of these accidents take place.
Recapping after use, or more accurately, positioning the cap prior to recapping after use, is the most common mechanism of injury. In positioning the cap, the hand holding the cap is moved toward the hand holding the contaminated needle. Bringing the hand holding the cap toward the needle is a movement distinct from, and occurring prior to, the more precise and thoughtfully executed recapping process itself. Since greater distances and tolerances for error are involved in positioning the cap prior to recapping, it is often performed nonchalantly, without deliberation and careful attention, sometimes with disastrous consequences.
Because the process of getting the cap back on the device after use results in so many punctures of the hand holding the cap, the Center for Disease Control has recommended that syringe devices be disposed of after use without replacing the cap.
But an article appearing in the Aug. 4th, 1988 edition of the New England Journal of Medicine recognizes that leaving needles uncapped is not an adequate solution. Although failing to recap a needle would certainly reduce recapping accidents, many other accident sequences occur precisely because the used needles involved are in an uncapped condition. If needles withdrawn from patients are simply left uncapped as a matter of course, the frequency of accidental encounters with needles intentionally left uncapped will increase as the frequency of recapping accidents declines.
The article suggests that safer syringe design is a better solution than not recapping. Such design should be an integral part of the device and should allow capping to take place while keeping hands out of harm's way.
The Center for Disease Control itself recognizes the value of bringing innovation of design to bear on the problem when it says in its published guidelines to prevent the spread of AIDS and hepatitis B, "Whenever possible, the employer should identify devices and other approaches to modifying the work environment which will reduce exposure risk."
The National Academy of Sciences Committee on Trauma Research has categorically stated that improvement in product design is among the best of the ways available to reduce puncture injuries to health care workers.
3. Discussion of Prior Art
Most design proposals intended to make hand-held hypodermic needle and syringe devices, herein sometimes called "hypo units" for brevity, safer to use and dispose of can be categorized according to one of four general approaches, each of which suffers serious drawbacks.